The goal of this program of research is to document the process by which individual differences in patterns of attention and emotion arise developmentally in infants' social relationships with mothers during the first three years of life. One of our proposed research designs -- called a relational-historical approach -- differs from population studies because we propose to track within normally developing mother-infant dyads the process of developmental change by making frequent observations (daily, weekly or monthly) across key developmental transitions related to the coupling between positive emotion, attention, and communication. We focus on four key developmental transitions in the first two years of life: the onset of social smiling at 2 months, the onset of interest in objects and focused attention at 4 months, the onset of shared attention and emotion at 12 months, and the onset of self-related attention and emotions at 18 months. A second proposed research design, based on a larger population of dyads, is used in order to generalize our process research findings to groups that are a cross-section of the US population and groups that are potentially at risk for developmental disorders. Our goal here is to discover whether between dyad differences in creativity of interpersonal communication are associated, within and across ages, with indices of positive emotion and flexible attention to everyday communication tasks. Finally, we propose to develop new methods for the study of change processes using a narrative approach. In summary, the proposed research has the following specific aims: (1) To study the process of development of individual differences in the coupling of infant attention and emotion in the context of the mother-infant communication system using a relational-historical approach; (2) To generalize our findings to a larger and more diverse population using a longitudinal follow-up study; and (3) To exploit new techniques for the investigation of key dynamic processes that regulate developmental change and the origins of individual differences in attention-emotion couplings.